Pollen identification of three notorious illicit drug plants and its potential applications in forensic practice.

Opium poppy, coca and cannabis are raw materials for three notorious illicit drugs. For a long time, drug lords have been growing and smuggling these drugs in a variety of ways and channels and are continually finding new ways of trafficking their wares, which has led to the increasing difficulty of global drug enforcement. In the present paper, we propose an innovative pollen identification system for these important drug plants, which provides a tool for screening and detection of the drugs to aid in drug enforcement. By utilizing the characteristics of these fine particles, their abundant production, and high resistance to decay, we believe this tool could be applied in the following scenarios: detecting and dynamically monitoring drug cultivation activities; determining whether a suspect has been to fields of drug plants and determining whether the site has ever been planted with a drug plant and/or was involved in drug production. In the future, combined with microscope automatic image acquisition technology and intelligent image recognition technology, this pollen identification system is expected to be used to screen three notorious illicit drug plants, thus enhancing the efficiency of drug related crime investigations.

The CDK4/6 Inhibitor Palbociclib Induces Cell Senescence of High-grade Serous Ovarian Cancer Through Acetylation of p53.

Cell senescence is an anti-cancer strategy following DNA repair and apoptosis, which is associated with the initiation, progression, and treatment of ovarian cancer. The CDK4/6 inhibitor alters cell cycle and induces cell senescence dependent on retinoblastoma (RB) family proteins. Objective Herein, we aimed to explore the effects of Palbociclib (a CDK4/6 inhibitor) on cellular senescence of high-grade serous ovarian cancer (HGSOC). Cell viability and cell cycle were evaluated by cell counting kit-8 and flow cytometry. Cell senescence was analyzed using the SA-ß-gal staining assay. The senescence-associated secretory phenotype was assessed using quantitative PCR (qPCR). Senescence-related markers were tested using western blot. The role of Palbociclib in vivo was clarified using xenograft tumor. Acetylation of p53 was evaluated by qPCR and western blot. The results showed that Palbociclib inhibited cell viability, blocked cell cycle at G0/G1 phase, and induced cell senescence. A rescue study indicated that knockdown of p53 reversed the effects on cell cycle and senescence induced by Palbociclib. Moreover, we found that Palbociclib promotes P300-mediated p53 acetylation, thus increasing p53 stability and transcription activity. Moreover, Palbociclib suppressed tumor growth in vivo with increased p53 and acetylated p53 levels. In conclusion, Palbociclib induced cell senescence of HGSOC through P300-mediated p53 acetylation, suggesting that Palbociclib may have the effect of treating HGSOC.

Bidirectional enhancement of Li2S redox reaction by NiSe2/CoSe2-rGO heterostructured bi-functional catalysts.

The high activity barriers of Li2S nucleation and deposition limit the redox reaction kinetics of lithium polysulfides (LiPSs), meanwhile, the significant shuttle effect of LiPSs hampers the advancement of Li-S batteries (LSBs). In this work, a NiSe2/CoSe2-rGO (NiSe2/CoSe2-G) sulfur host with bifunctional catalytic activity was prepared through a hard template method. Electrochemical experiment results confirm that the combination of NiSe2 and CoSe2 not only facilitates the bidirectional catalytic function during charge and discharge processes, but also increases the active sites toward LiPSs adsorption. Simultaneously, the highly conductive rGO network enhances the electronic conductivity of NiSe2/CoSe2-G/S and provides convenience for loading NiSe2/CoSe2 catalysts. Benefitting from the exceptional catalytic-adsorption capability of NiSe2/CoSe2 and the presence of rGO, the NiSe2/CoSe2-G/S electrode exhibits excellent electrochemical properties. At 1C, it demonstrates a low capacity attenuation of 0.087 % per cycle during 500 cycles. The electrode can maintain a discharge capacity of 927 mAh/g at a sulfur loading of 3.3 mg cm-2. The bidirectional catalytic activity of NiSe2/CoSe2-G offers a prospective approach to expedite the redox reactions of active S, meanwhile, this work also offers an ideal approach for designing efficient S hosts for LSBs.

Visual Color Change During Spin-coating Guiding the Quality of Cu2 ZnSn(S,Se)4 Films.

Solution method provides a low-cost and environmentally friendly route for the fabrication of Cu2 ZnSn(S,Se)4 (CZTSSe) thin-film solar cells. However, uncontrollable quality of the CZTSSe absorber layer will severely limit the device's performance. In this study, it is find that the thickness and the quality of the formed precursor is not stable because of the variation of the viscosity of the precursor solution. Combined by different characterization methods, the results disclose that such change is strongly related to the reflected color of the first coating layer during precursor growth. Further studies disclose that only by maintaining the appropriate reflected color can a well-crystallized CZTSSe film be prepared, thereby obtaining good solar cell efficiency. This semi-empirical pattern is confirmed by thin-film interference theory. Under the guidance of this method, CZTSSe absorbers with high quality are obtained easily, and the highly efficient CZTSSe solar cell can be fabricated easily. This study provides a feasible and effective strategy to obtain the optimal structure and composition of CZTSSe film toward the production of highly efficient kesterite solar cells, which can also be widely applied to the preparation of other films by solution-based method.

Correlation between Triclosan (TCS) exposure and endometriosis.

Objective: To study the correlation of Triclosan (TCS) exposure with typing and staging of endometriosis, and with other potential influencing factors. Methods: This was a retrospective study. Thirty two patients that were diagnosed with endometriosis by laparoscopy or surgery in Taicang First People's Hospital from May 2020 to December 2021 were enrolled in the endometriosis group, and patients who were confirmed free of endometriosis by surgeries for other purposes during the same period were enrolled as the control group. All blood samples were tested twice in two different vials. The association of TCS exposure level with occurrence, staging, typing of endometriosis, and income of the patients were analyzed. Results: Patients with endometriosis had significantly higher TCS exposure levels than the control group. TCS exposure level in patients with endometriosis was positively correlated with patient income), and was significantly higher in patients with Stage-IV endometriosis than in those with Stage-III and II diseases. TCS exposure levels showed no significant difference among patients with ovarian type, ovarian + peritoneal type, and deep nodular type endometriosis TCS exposure level in patients with endometriosis was positively correlated with the staging of the disease. TCS exposure was highly positively correlated with the staging of the disease in patients with ovarian type endometriosis and in patients with deep nodular endometriosis, but there's no such correlation in patients with ovarian + peritoneal type endometriosis. Conclusion: TCS exposure level in endometriosis patients was higher than that in normal women, and is positively correlated with endometriosis staging and income of the patients.

Metal-organic frameworks as solid-phase microextraction adsorbents for the determination of triacetone triperoxide by gas chromatography-mass spectrometry.

Triacetone triperoxide (TATP) is a high-power explosive which is often used by criminals. The detection of TATP is of great significance for solving the explosion cases. However, the preconcentration and analysis of trace levels of TATP still pose challenges for analytical researchers. In this study, metal-organic frameworks (MOFs), including IRMOF-8, MOF-5, UIO-66, ZIF-8, and MIL-101(Cr), were immobilized on a stainless steel wire using a physical adhesive method as a solid-phase microextraction (SPME) fiber coating. The prepared fibers with a controllable thickness were used for the extraction of TATP followed by gas chromatography-mass spectrometry (GC-MS) analysis. Under the identical experimental conditions, the IRMOF-8-coated fiber exhibited higher extraction efficiency for TATP than the other fibers. The IRMOF-8-coated fiber was then characterized using scanning electron microscopy and thermogravimetric analysis. The results indicated that the IRMOF-8-coated fiber not only had good thermal and chemical stabilities but also afforded a high TATP extraction efficiency. Under the same extraction conditions, the extraction efficiency of the IRMOF-8-coated fiber was 2-8 times higher than those of commercial fibers. The limit of detection was 13 ng/mL, and linearity was observed in the range of 50-5000 ng/mL with a correlation coefficient greater than 0.998. The intraday repeatability (n = 6), interday repeatability (n = 3), and fiber-to-fiber reproducibility (n = 3), were 4.1 %, 4.8 %, and 8.0 %, respectively. The recoveries of TATP from the simulated tap water and soil samples were 87.32-90.57 % and 88.76-100.93 %, respectively, with relative standard deviations lower than 11.11 % (n = 3). The above method was successfully applied for the detection of TATP transferred from a finger to a paper surface, demonstrating its good application prospects in the analysis of trace TATP.

Application of lead isotope signature and likelihood ratio evaluation in a shooting incident investigation.

Bullet projectiles are often found in shooting crime scenes and can help identify the cartridges used in shooting events. The most conclusive way to link a fired projectile to a firearm is by identifying the unique markings of the barrel on the projectile or case. But in circumstances where the investigation of striation marks is impossible, lead isotope ratio signature analysis of projectile fragments can facilitate building the linkage of the suspect, the cartridge used and the victim. This work presents a shooting incident happened in a hunting field, where a hunting guide was shot to death. A tiny lead projectile fragment was collected from the victim's head. Pb isotope ratios measured by laser ablation multicollector inductively coupled plasma mass spectrometry (LA-MC-ICPMS) were used to make comparisons between the fragment and the shots seized from two suspects. Additionally, a reference dataset comprising 50 lead bullet projectiles from various manufacturers was characterized using LA-MC-ICPMS. The evaluation of the comparison was carried out by multivariate likelihood ratio (LR) computations based on the reference dataset. The lead isotope ratio and likelihood ratio evaluation methods helped infer the source of the fragment and were highly supportive in the shooting incident investigation.

Early life growth and developmental trajectory in children with biliary atresia undergoing primary liver transplantation.

Objective: To clarify the early growth and developmental characteristics of children with biliary atresia (BA) undergoing primary liver transplantation (pLT). Methods: A prospective cohort study, which specifically focused on BA-pLT children, was conducted after the diagnosis of BA by following the children at the time of pLT and 1, 3, 5, 7 months and 1 year after pLT for growth and developmental monitoring. The growth parameters were calculated according to the WHO standard, and the developmental status was assessed using Denver Developmental Screening Tests. Results: A total of 48 BA children who received pLT at the age of 5.00 ± 0.94 months were analyzed. The weight-for-age Z-value (ZW) and length-for-age Z-value (ZL) were higher than the head circumference-for-age Z-value (ZHC) at pLT (P = 0.002 and 0.02), but they were all lower than the WHO growth standard (Z = 0) (P < 0.001). The ZW and ZHC decreased first and then returned to the population level at 1 year after pLT, while the ZL only returned to the preoperative status and was lower than the ZW and ZHC (P < 0.001). Developmental screening showed that 35% (17/48) of the children were defined as suspicious and 15% (7/48) were abnormal at 1-4 months after pLT, the most likely time to be suspected of developmental delay. At 1 year after pLT, gross motor skill delay still existed (12/45, 27%), and language skill delay began to appear (4/45, 9%). Conclusions: BA-pLT children suffer from growth and developmental problems. Low ZHC is the main growth problem before pLT, while low ZL is the problem after pLT. Developmental delays are significant after pLT, especially in motor and language skills. The current study suggested that further studies are warranted to clarify the long-term growth and developmental outcomes of BA-pLT children, to compare them with children undergoing the Kasai procedure and to explore their influencing factors and possible mechanisms.

Impact of physical and mental fatigue on construction workers' unsafe behavior based on physiological measurement.

INTRODUCTION: Construction worker fatigue is an important factor leading to unsafe behavior, a major cause of construction accidents. Uncovering the impact mechanism of fatigue on workers' unsafe behavior can prevent construction accidents. However, it is difficult to effectively measure workers' fatigue onsite and analyze the impact of worker fatigue on their unsafe behavior. METHOD: This research analyzes the relationship between the physical and mental fatigue of construction workers and their unsafe behavior via physiological measurement based on a simulated experiment on handling tasks. RESULTS: It is found that: (a) both physical fatigue and mental fatigue have negative effects on workers' cognitive ability and motion ability, and the negative effects are more serious under the combination of the two types of fatigue; (b) mental fatigue can easily change workers' risk propensity, making them more willing to face risks, and in a state of the two types of fatigue, they are more likely to make choices with less pay and higher risk; (c) the number of signal identification errors is positively correlated with LF (low frequency)/HF (high frequency), and negatively correlated with the standard deviation of normal-to-normal intervals (SDNN), while the number of footstep control errors is negatively correlated with the time elapsed between two successive R waves (RR interval) and skin temperature (SKT). PRACTICAL APPLICATIONS: These findings can enrich construction safety management theory from a perspective of quantified fatigue and facilitate safety management practices on construction sites, thus contributing to the body of knowledge and practices of construction safety management.

Roxadustat (FG-4592) abated lipopolysaccharides-induced depressive-like symptoms via PI3K signaling.

Background: Despite its role in inflammation and the redox system under hypoxia, the effects and molecular mechanisms of hypoxia-inducible factor (HIF) in neuroinflammation-associated depression are poorly explored. Furthermore, Prolyl hydroxylase domain-containing proteins (PHDs) regulate HIF-1; however, whether and how PHDs regulate depressive-like behaviors under Lipopolysaccharides (LPS)-induced stress conditions remain covered. Methods: To highlight the roles and underlying mechanisms of PHDs-HIF-1 in depression, we employed behavioral, pharmacological, and biochemical analyses using the LPS-induced depression model. Results: Lipopolysaccharides treatment induced depressive-like behaviors, as we found, increased immobility and decreased sucrose preference in the mice. Concurrently, we examined increased cytokine levels, HIF-1 expression, mRNA levels of PHD1/PHD2, and neuroinflammation upon LPS administration, which Roxadustat reduced. Furthermore, the PI3K inhibitor wortmannin reversed Roxadustat-induced changes. Additionally, Roxadustat treatment attenuated LPS-induced synaptic impairment and improved spine numbers, ameliorated by wortmannin. Conclusion: Lipopolysaccharides-dysregulates HIF-PHDs signaling may contribute to neuroinflammation-coincides depression via PI3K signaling.

[Applications of functional materials-based solid phase microextraction technique in forensic science].

Sample extraction is a crucial step in forensic analysis, especially when dealing with trace and ultra-trace levels of target analytes present in various complex matrices (e. g., soil, biological samples, and fire debris). Conventional sample preparation techniques include Soxhlet extraction and liquid-liquid extraction. However, these techniques are tedious, time-consuming, labor-intensive and require large amounts of solvents, which poses a threat to the environment and health of researchers. Moreover, sample loss and secondary pollution can easily occur during the preparation procedure. Conversely, the solid phase microextraction (SPME) technique either requires a small amount of solvent or no solvent at all. Its small and portable size, simple and fast operation, easy-to-realize automation, and other characteristics thus make it a widely used sample pretreatment technique. More attention was given to the preparation of SPME coatings by using various functional materials, as commercialized SPME devices used in early studies were expensive, fragile, and lacked selectivity. Examples of those functional materials include metal-organic frameworks, covalent organic frameworks, carbon-based materials, molecularly imprinted polymers, ionic liquids, and conducting polymers, all widely used in environmental monitoring, food analysis, and drug detection. However, these SPME coating materials have relatively few applications in forensics. Given the high potential of SPME technology for the in situ and efficient extraction of samples from crime scenes, this study briefly introduces functional coating materials and summarizes the applications of SPME coating materials for the analysis of explosives, ignitable liquids, illicit drugs, poisons, paints, and human odors. Compared to commercial coatings, functional material-based SPME coatings exhibit higher selectivity, sensitivity, and stability. These advantages are mainly achieved through the following approaches: First, the selectivity can be improved by increasing the π-π, hydrogen bonds, and hydrophilic/hydrophobic interactions between the materials and analytes. Second, the sensitivity can be improved by using porous materials or by increasing their porosity. Third, thermal, chemical, and mechanical stability can be improved by using robust materials or fixing the chemical bonding between the coating and substrate. In addition, composite materials with multiple advantages are gradually replacing the single materials. In terms of the substrate, the silica support was gradually replaced by the metal support. This study also outlines the existing shortcomings in forensic science analysis of functional material-based SPME techniques. First, the application of functional material-based SPME techniques in forensic science remains limited. On one hand, the analytes are narrow in scope. As far as explosive analysis is concerned, functional material-based SPME coatings are mainly applied to nitrobenzene explosives, while other categories, such as nitroamine and peroxides, are rarely or never involved. Research and development of coatings is insufficient and the application of COFs in forensic science has not yet been reported. Second, functional material-based SPME coatings have not been commercialized as they don't yet have inter-laboratory validation tests or established official standard analytical methods. Therefore, some suggestions are proposed for the future development of forensic science analyses of functional material-based SPME coatings. First, research and development of functional material-based SPME coatings, especially fiber coatings with broad-spectrum applicability and high sensitivity, or outstanding selectivity for some compounds, is still an important direction for SPME future research. Second, a theoretical calculation of the binding energy between the analyte and coating was introduced to guide the design of functional coatings and improve the screening efficiency of new coatings. Third, we expand its application in forensic science by expanding the number of analytes. Fourth, we focused on the promotion of functional material-based SPME coatings in conventional laboratories and established performance evaluation protocols for the commercialization of functional material-based SPME coatings. This study is expected to serve as a reference for peers engaged in related research.

Predicting volatility in natural gas under a cloud of uncertainties.

The COVID-19 pandemic has triggered an economic crisis and the ensuing global uncertainty. The current Russian-Ukrainian conflict has escalated tensions in various regions and increased various uncertainties in the financial and economic system. These uncertainties have had a significant impact on the development of the natural gas market during the current critical period of carbon neutrality and energy transition. This paper explores the impact of various uncertainties on price volatility in the U.S. natural gas futures market using the GARCH-MIDAS model. We considered eleven types of uncertainties, including four US economic policy uncertainties, four global uncertainty indicators, and oil supply-demand uncertainty closely related to the natural gas market. The in-sample empirical results find that various uncertainties can impact the natural gas market. However, through out-of-sample testing, we find that economic policy uncertainty has more predictive power than other indicators in predicting natural gas price fluctuations. Interestingly, oil supply-demand uncertainty surpasses global indicators and can provide forecasting information for natural gas markets. Therefore, in the current context of high uncertainty, our research may offer better decision-making opinions for market participants.

Dendritic spine dynamics in associative memory: A comprehensive review.

Associative learning and memory are fundamental behavioral processes through which organisms adapt to complex environments. Associative memory involves long-lasting changes in synaptic plasticity. Dendritic spines are tiny protrusions from the dendritic shaft of principal neurons, providing the structural basis for synaptic plasticity and brain networks in response to external stimuli. Mounting evidence indicates that dendritic spine dynamics are crucial in different associative memory phases, including acquisition, consolidation, and reconsolidation. Causally bridging dendritic spine dynamics and associative memory is still limited by the suitable tools to measure and control spine dynamics in vivo under behaviorally relevant conditions. Here, we review data providing evidence for the remodeling of dendritic spines during associative memory processing and outline open questions.

Toward High Efficient Cu2 ZnSn(Sx ,Se1- x )4 Solar Cells: Break the Limitations of VOC and FF.

Increasing the fill factor (FF) and the open-circuit voltage (VOC ) simultaneously together with non-decreased short-circuit current density (JSC ) are a challenge for highly efficient Cu2 ZnSn(S,Se)4 (CZTSSe) solar cells. Aimed at such target in CZTSSe solar cells, a synergistic strategy to tailor the recombination in the bulk and at the heterojunction interface has been developed, consisting of atomic-layer deposited aluminum oxide (ALD-Al2 O3 ) and (NH4 )2 S treatment. With this strategy, deep-level CuZn defects are converted into shallower VCu defects and improved crystallinity, while the surface of the absorber is optimized by removing Zn- and Sn-related impurities and incorporating S. Consequently, the defects responsible for recombination in the bulk and at the heterojunction interface are effectively passivated, thereby prolonging the minority carrier lifetime and increasing the depletion region width, which promote carrier collection and reduce charge loss. As a consequence, the VOC deficit decreases from 0.607 to 0.547 V, and the average FF increases from 64.2% to 69.7%, especially, JSC does not decrease. Thus, the CZTSSe solar cell with the remarkable efficiency of 13.0% is fabricated. This study highlights the increased FF together with VOC simultaneously to promote the efficiency of CZTSSe solar cells, which could also be applied to other photoelectronic devices.

Lead isotope measurement of primer gunshot residues and likelihood ratio predictions for forensic cartridge discrimination and individualization in China.

Gunshot residues (GSR), cartridge projectiles, and casings are frequently encountered evidence in gun-related forensic investigations. However, in circumstances where the investigation of striation marks is impossible, such as unrecovered or deformed projectiles and cartridge casings, GSR deposited on the hands or clothes of the shooter and victim-related items can provide information to establish a link between the suspect, the firearms used, and the victim. Since the formula of primers used by all cartridge manufacturers in China is identical, links based on the conventional morphological and compositional analysis of GSR are difficult to establish. However, the abundance of lead isotopes in primer components of lead styphnate varies significantly, and a fundamental understanding of these differences may facilitate the validation of primer (p)GSR evidence in forensic investigations. Here, 44 pGSR samples were characterized by Pb isotope ratios of 206 Pb/204 Pb, 207 Pb/204 Pb, and 208 Pb/204 Pb using laser ablation multicollector inductively coupled plasma mass spectrometry. There was no obvious mass fractionation of the lead isotope ratios of the primers from individual cartridges analyzed before and after the shooting process, thereby establishing a basis for the comparison of pGSR and unfired cartridges. Evaluation of the results using univariate likelihood ratio (LR) computations revealed low rates of misleading evidence (<0.53%) The results demonstrated that lead isotope ratio analysis of pGSR and LR predictions can provide a practicable method for forensic cartridge discrimination and individualization.

Determination of disperse dyes on polyester fibers by UHPLC-Orbitrap MS.

The determination of fiber dyes is important in forensic investigations. Although a variety of fiber dyes detection methods have been established, the sensitive and accurate determination of trace fiber dyes remains a challenge due to the possible interferences caused by complex environmental matrix and various fiber additives. Orbitrap mass spectrometry (Orbitrap MS) is a type of high-resolution mass spectrometry with high qualitative accuracy and detection sensitivity which highly meet the identification requirements of fiber dyes in real cases. However, the application of Orbitrap MS in fiber dye analysis is limited. In this regard, this study used polyester fiber, which is the most commonly-found fiber in forensic cases, as a model and established a UHPLC-Orbitrap MS method to analyze disperse dyes on polyester fibers. Using the optimized UHPLC-Orbitrap MS method, nine disperse dyes were accurately identified and well separated, and the limits of detection ranged between 0.1 ng/mL and 5.0 ng/mL. The developed method was applied to analyze actual fiber samples, and dyes from single fibers of 1 mm in length could be accurately detected. The established method is sensitive, accurate, and demonstrates good application prospects.

Mineralogical and elemental data for soil discriminating and geolocation tracing.

One of the key tasks of soil analysis in forensic sciences is to provide information about its diversities and geolocation. In fact, soil analysis is relevant for forensic geologists. In this study, a total of 80 soil samples were collected from eight Chinese cities (10 samples per city). Different minerals and their relative percentages were analyzed by the X-ray diffraction (XRD) method. In addition, the relative amounts of montmorillonite, kaolinite, amphibole, feldspar, calcite, and dolomite provided information about the origin of a soil, either if it came from a northern or southern city of China. The oxide weight percentages of 10 elements of Al2O3, SiO2, Fe2O3, K2O, Na2O, MgO, CaO, P2O5, MnO, and TiO2 were also obtained by using X-ray fluorescence (XRF) from the 80 soil samples. Moreover, principal component analysis (PCA) and hierarchical clustering analysis (HCA) methods were performed for dimensionality reduction, elemental marker identification and soils classification to the city they came from purposes. The eighty soils analyzed in this study could be tracked correctly to their city of origin. The K-Nearest Neighbors (KNN) model was done to evaluate the prediction ability based on the soil elemental composition, and it was confirmed by cross validation methods. The results demonstrated that mineralogical and elemental composition can provide powerful information for soil discrimination and source tracing.

Optimizing safety-measure combinations to address construction risks.

Objectives. Most methods used to develop construction risk responses address the risk-mitigation optimization problem by solving the objective functions. They are passively achieved by satisfying constraint conditions, which are not adequate for efficient construction management. This study aims to provide an active optimization strategy for selecting risk responses. Methods. We combined set pair analysis (SPA) with the technique for order preference by similarity to an ideal solution (TOPSIS) to control the construction risks to an acceptable level instead of excessively to the minimum level. SPA is employed to assess the pre-mitigation and post-mitigation risk levels based on the uncertainty theory, and the TOPSIS is used to rank safety measures based on their risk-mitigation effects. A case study of concrete pumping for a super high-rise building was used to exemplify how the proposed optimization model assists risk control and to validate its reasonability. Conclusion. The developed TOPSIS-SPA-based method figures out the optimal safety-measure combination reducing construction risks economically to an acceptable level with the fewest number of measures. The findings can assist decision-makers in formulating cost-effective risk-control schemes.

Determination of stable nitrogen isotopic ratios of nitrate ions in ammonium nitrate.

Ammonium nitrate (AN) is one of the most commonly used explosives in criminal cases. The comparison and source-tracing of AN is important for investigation of attribution and fingerprinting of an explosive used at different events. The stable isotope signature of AN is an important index for comparison and tracing. However, the characteristics of the stable nitrogen isotopic ratios of AN (δ15 NNH4NO3 ) alone are not sufficient to achieve a fine comparison between different AN samples. To increase the comparison index and further improve the discriminability between stable nitrogen isotopic ratios of different ANs, a method of isolation and analysis of nitrate ions in AN was established using stable-isotope-ratio mass spectrometry (IRMS). The method was based on the principle that strong alkali react with AN to produce ammonia and nitrate. After the isolation, stable nitrogen isotopes of nitrate ions (δ15 NNO3 ) were obtained using IRMS, and then the stable nitrogen isotopes of ammonium ions from AN (δ15 NNH4 ) was calculated according to the principle of mass balance. The results show that the method is effective for the isolation of nitrate ions without notable isotope fractionation. The developed method was applied to analyze and discriminate AN samples from eight different cities in China. Three samples out of the initial eight AN samples with similar δ15 NNH4NO3  values were further distinguished by their δ15 NNH4 and δ15 NNO3  values. The isolation and stable-nitrogen isotopic analysis method developed for nitrate ions in AN is simple and effective, thereby increasing the discriminability of the stable isotope ratios in AN.

A case study in forensic soil comparison.

Soil examination can provide useful forensic information about the spatial location and suspect's activities. Many techniques have been applied for soil comparison and provenance determination in criminal investigations. Pollen and diatom identification, which has the potential to provide an independent ecological assessment of soil evidence, is currently underused in forensic soil analysis. This work presents a case study of application of these methods to help criminal investigation in a murder case, which happened in an irrigation ditch in Hunan Province, southern China. Soils from the suspect's clothes, the exact crime scene spot in the irrigation ditch, along the ditch and the reference ditches were collected and analyzed. In addition to the element and mineral analysis, pollen and diatom assemblages were analyzed for further comparison. The statistical methods of hierarchical cluster and cosine similarity analysis were carried out to assist in soil comparison and provenance determination. The results showed that soil on the suspect's clothes had a high probability to share the same source with the soil from the crime scene in the irrigation ditch. The suspect confessed to murder based largely on the soil examination result even without other evidences.